Expert and art historian Meike Hoffmann from the Berlin Free University speaks during a news conference in Augsburg, Germany, on Tuesday. / Kerstin Joensson, AP

by Jennifer Collins and Jesse Singal , Special for USA TODAY

by Jennifer Collins and Jesse Singal , Special for USA TODAY

BERLIN - German authorities defended themselves from accusations that they covered up the discovery of more than 1,400 artworks - including pieces by Pablo Picasso and Henri Matisse - seized during the Nazi reign.

"Our primary goal is to investigate whether there has been a crime," Reinhard Nemetz, head of the Augsburg state prosecutor's office, said at a news conference on Tuesday.

He said it would have been "counterproductive" to have gone public with the case.

"It is by no means easy to find the rightful owners, particularly when we are talking about over 1,400 paintings," he said.

That explanation did not satisfy people who have been trying to find artwork looted by the Nazis and their collaborators in Europe and return it to its rightful owners or their heirs.

"The fact that this is a year and a half later is as much an issue as the find itself," Anne Webber, of the London-based Commission for Looted Art, told USA TODAY. "There needs to be a transparency, there needs to be a commitment to providing a detailed list.

"And if the works turn out to be looted, there needs to be a clear and simple claims procedure," she said.

The find was made public not by the German government but by reporters for the German news magazine Focus. The works of art, which included previously unknown works from Marc Chagall and Otto Dix, were found in the Munich apartment of Cornelius Gurlitt, 79, whose father Hildebrand Gurlitt was a wartime art dealer.

Focus said Cornelius Gurlitt had funded himself by occasionally selling artworks, and he had a bank account containing $674,000. He attracted the suspicion of authorities in late 2010 when they found him traveling from Zurich to Munich with a large amount of cash.

Hildebrand Gurlitt was a collector of the modern art of the early 20th century that the Nazis branded as un-German or "degenerate" and removed from show in state museums.

Nazi propaganda minister Joseph Goebbels recruited Gurlitt to sell the "degenerate art" abroad to try to earn cash for the state. Gurlitt bought some for himself and also independently bought art from desperate Jewish dealers forced to sell.

Chancellor Angela Merkel's spokesman Steffen Seibert said the government was informed "several months ago" about the case. He said authorities in Berlin were supplying "advice from experts in the field of so-called 'degenerate art' and the area of Nazi-looted art."

German authorities said the artwork, which included both modern paintings and others dating to the 16th century, had been discovered in March 2012 and not 2011 as reported by Focus.

Authorities said they found 121 framed and 1,285 unframed works - including by 20th-century masters such as Picasso, Chagall, Max Liebermann and Ernst Ludwig Kirchner and earlier works by artists including Henri de Toulouse-Lautrec, Gustave Courbet, Auguste Renoir and Canaletto. The oldest work dates to the 16th century.

Prosecutor Reinhard Nemetz told reporters in the Bavarian city of Augsburg that investigators have turned up "concrete evidence" that at least some of the works were seized by the Nazis from their owners or classed by them as "degenerate art" and seized from German museums in 1937 or shortly after.

Analysts involved in the investigation said the artworks were in good condition.

"When you stand in front of works and see these long lost works, that were thought to have been destroyed, in good condition, that is such a happy feeling," said Meike Hoffmann, a professor at the Free University of Berlin's art history department, during the news conference.

"The pictures are of extraordinary quality and are of huge scientific value. Many works were not known before."

That did not satisfy many critics who said the German government should have made the find public long ago and should publish a list of the artworks, which it has yet to do.

"This case shows the extent of organized art looting which occurred in museums and private collections," said Ruediger Mahlo, of the Conference on Jewish Material Claims Against Germany, noting private collections were almost all Jewish.

"We demand the paintings be returned to their original owners," he told Israel Hayom newspaper. "It cannot be, as in this case, that what amounts morally to the concealment of stolen goods continues."

Mahlo criticized the lack of transparency in dealing with the case and said it was typical of the attitude toward looted art, which for some Jewish families constitutes the last personal effects of relatives murdered during the Holocaust.

Germany is a signatory to the Washington Conference Principles on Nazi-Confiscated Art, which calls for as much transparency as possible in identifying and locating Nazi-seized art.

"There is an issue in Germany, which is that there is a great reluctance to publish lists of looted works of art," said Webber.

She said that there had also been problems with the pace of such investigations, which had become a concern for families whose elderly members - the owners of the artwork - are dying out.

Webber cited the example of the German director-general of the Bavarian State Painting Collections, who had announced 13 years ago that investigations would begin on between 4,000 and 7,000 artworks acquired by a major art museum in Munich during the Nazi period. It took 11 years for a lead researcher to be appointed to the task.

Even when institutions are quick to launch investigations, Webber said there are serious logistical obstacles to identifying and tracking down stolen works of art.

"It's a very long and complicated process to trace the looted artwork because they're in public collections or in private collections," she said.

"It depends on when they come up for sale, it depends whether the public collections have undertaken provenance research they've committed to doing or whether they've published their collections at all. Despite looking for art absolutely painstakingly, in a very detailed and painstaking way, some 90% of those paintings are still missing."